JP3006227B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning device for writing a light beam of image information on a photosensitive drum or the like in an image forming apparatus such as a laser printer or a digital electronic copying machine. The present invention relates to a motor in which a rotor magnet constituting a motor for driving a motor is formed in a disk shape, and the rotor magnet is directly attached to a rotating shaft without using a rotor member, thereby simplifying the configuration of the motor.

[0002]

2. Description of the Related Art In an image forming apparatus such as a laser printer or a digital type electronic copying machine, an LED is controlled by image information output from an image information output device such as a computer or image information such as light obtained by scanning a document. And the like are emitted. In the image forming apparatus, the surface of an image carrier such as a photosensitive drum is scanned by the laser beam to write image information. Further, in the image forming apparatus such as a laser printer, a mechanism for forming a toner image on an image carrier such as a photosensitive drum is provided by using an electrophotographic method, as in a general electronic copying machine or the like. An electrostatic latent image is formed on the photosensitive drum by irradiating a laser beam, and a toner image is formed by attaching toner to the electrostatic latent image.

An apparatus for writing image information on a photosensitive drum by the laser beam is disclosed in, for example, Japanese Patent Laid-Open No. 2-2.
An apparatus such as that disclosed in Japanese Patent No. 30269 is known. In the conventional apparatus, means for writing an image in the width direction of a photosensitive drum by polarizing a laser beam by a rotating polygon mirror is used. Used. In the above-described conventional scanning device, for example, a scanning device 1 as shown in FIG. 3 is used.

In the scanning device 1, a laser beam output from a light source such as a semiconductor laser (not shown) is reflected on a mirror surface of a rotating polygon mirror 11 provided in a rotating device 10, and the rotating polygon mirror 11 operates at high speed. , The reflected laser beam 8 scans the photosensitive drum 9 in the width direction. The rotary polygon mirror 11 is disposed inside the optical box 2 with the upper surface of the optical box 2 covered with the cover 5, and is driven at a high speed by the rotating device 10. Then, the laser beam reflected on the mirror surface of the rotating polygon mirror 11 is applied to the imaging lens group 6 and the glass 7 provided at the end of the box.
And forms an image on the surface of the photosensitive drum 9.

In the scanning apparatus 1 as shown in FIG. 3, in order to drive the rotary polygon mirror 11 at a high speed, Japanese Patent Application Laid-Open No. 63-204224 and Japanese Patent Application Laid-Open No.
A driving device such as that disclosed in Japanese Patent Application Laid-Open Publication No. Sho 64-66615 or the like is used. Further, in addition to the above-mentioned conventional example, a driving device as disclosed in Japanese Patent Application Laid-Open No. 2-309066 may be used. JP-A-2-3
In the example shown in Japanese Patent Publication No. 09066, as shown in FIG. 4, the frame of the driving device of the rotating device 10 is constituted by the optical box 2, and the base member 2 a of the optical box 2 has a fixed shaft 15. Is fixedly held by a lower set screw 16 and rotatably supports the rotating shaft member 20 with respect to the fixed shaft 15 via upper and lower bearings 19 and 19a. An upper ring 17 and a preload spring 18 are provided above the fixed shaft 15 to hold a bearing 19.

The rotating shaft member 20 rotatably supported on the fixed shaft 15 has a rotating polygon mirror 11 at an upper part and a rotor member 25 provided with a rotor magnet 30 at a lower part. Rotor magnet 30 provided in
And the stator coil 31 arranged in the optical box 2 constitute the motor 12. The rotor magnet 30 constituting the motor 12 is adhered to the lower surface of the rotor member 25. A stator coil 31 and a stator yoke 32 made of a magnetic material such as a silicon steel plate are provided in a groove 3 provided in the base member 2a. Are arranged.

[0007] A control circuit 35 is arranged for the stator coil 31, and a current is supplied at a predetermined pulse by switching (on / off) in the control circuit to drive the rotor magnet 30. When a current is applied to the stator coil 31 in the motor, a strong magnetic field is generated in the vertical direction in the drawing. However, by disposing the stator yoke 32 below the coil, the stator coil 3
1 is applied to the stator yoke 32
To return upward to perform the function of improving the efficiency of the motor.

In the driving device, an annular groove 26 is provided on the upper surface of the rotor member 25, and a balance weight 27 is attached to the groove 26.
The dynamic balance is adjusted. When the rotation speed of the drive motor 12 is 5000 to 8000 RPM, the rotating polygon mirror 11 and the rotor
In the case of the rotor 5 and the rotor magnet 30, it is not necessary to adjust the dynamic balance as long as the accuracy of the radial components is increased. In the case of 8000 to 12000 RPM, an annular groove is provided in the rotor member 25, and dynamic balance can be adjusted by correcting one surface by adding a balance weight to the groove. However, in particular, when the rotational speed exceeds 12000 RPM, it is required to reduce the vibration as the rotating polygon mirror is rotated at a high speed. Therefore, an annular groove is also provided on the upper surface of the rotating shaft member 20. It is necessary to adjust the dynamic balance precisely by taking measures such as attaching a counterweight also to the groove, so that the demand for precise scanning accuracy can be satisfied.

In the drive motor, in addition to the means for adjusting the dynamic balance, an upper ring 17 is provided on the fixed shaft 15 and a preload spring 18 is arranged between the upper shaft 17 and the bearing 19. Pressing downward. Further, a labyrinth seal is formed for the lower bearing 19a by the groove 4 provided in the base member 2a and the projection member at the lower part of the rotating shaft member 20, and the lubricating oil in the bearing is externally provided. Be prevented from flying. Further, the rotor member 25 and the rotary polygon mirror 11
, A spring 23 is arranged, and the rotating polygon mirror 11
Is pressed toward the upper portion 21 of the rotary shaft member 20 so that the rotary polygon mirror is rotated together with the rotary shaft member.
In addition to the above configuration, a seal plate 2
4 is disposed to perform a sealing action so that grease of the bearing does not scatter.

[0010]

In the rotating device constructed as described above, the rotor member is often made of iron, and its weight serves as a flywheel while adding a balance weight. For improving rotational accuracy. Further, as shown in FIG. 4, the rotor member supports a rare earth rotor magnet, reinforces the property that the rotor magnet is easily broken by centrifugal force due to rotation, and can safely support the magnet. However, the largest cause of the imbalance is in the rotor member.

However, when using a means for supporting the rotor magnet in combination with the iron rotor member, it is necessary to fix the magnet to the rotor member using an adhesive means. Even if the members are manufactured with high accuracy, it is troublesome to maintain the accuracy when combining them. Also, recently, it has become possible to create tough plastic magnets,
Even when rotating at high speed, the plastic magnet member can be used alone, but in the case of a motor with a very high rotation speed, such as an optical scanning device, avoid using it in combination with an iron rotor member. It cannot be done. Furthermore, high-precision integrated circuits for control have been developed that can control rotation without relying on the flywheel effect. However, drive motors such as optical scanning devices fully utilize such control means. There is a problem that they do not.

That is, in the rotating device shown in the above-mentioned conventional example, the manufacturing accuracy of each component is strictly controlled, and even if the components are accurately combined, the components are not Very many, the assembly is cumbersome. Also, when combining the rotor member and the rotor magnet, even if the dynamic balance of each member is accurately adjusted,
After combining them, it is necessary to adjust the dynamic balance again, and there is a problem that the adjustment for that also requires time.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problem caused by combining the above-mentioned rotor magnet with an iron rotor member, and using only the rotor magnet as a molded product without using the rotor member. An object of the present invention is to provide a device that simplifies the configuration of a motor by applying dynamic balance adjusting means to a magnet, and that can easily be assembled and adjusted.

[0014]

According to the present invention, there is provided a light source for outputting a light beam containing information, and a light source for polarizing the light beam in a predetermined direction to an image carrier such as a photosensitive drum in a width direction thereof. Optical scanning comprising a rotating polygon mirror for scanning light, a motor for driving the rotating polygon mirror, a rotor magnet supporting the motor on a shaft member, and a stator coil supported on a base member. Related to the device. The invention according to claim 1 of the present invention is configured such that the rotor magnet is formed of a member shaped into a disk shape, and a polygon mirror is arranged via a rotating shaft integrally provided with the rotor magnet, An annular groove for providing a balance weight for dynamic balance adjustment is provided on two surfaces perpendicular to the rotation axis.

[0015]

With the above-described structure, the drive motor of the optical scanning device according to the present invention does not use the iron rotor member conventionally used, but uses only the rotor magnet and the rotating shaft member. , The rotation mechanism can be simplified. In addition, since the iron rotor member is not used, it is possible to easily adjust the dynamic balance, and it is also possible to easily perform the assembling work of the device. Furthermore, when molding a rotor magnet made of plastic or the like, by forming the corners such as grooves into an arc shape, the strength of the member can be improved, and a rotating body that can withstand high-speed rotation is formed. can do.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical scanning device of the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 is a rotating device 10 having the same configuration as that shown in FIG. 4 described above, but the rotor magnet 40 constituting the motor 12 is replaced by a magnet without using a rotor member made of iron or the like. Is used. The rotor magnet 40 is integrally formed as a disk-shaped material by a plastic magnet. The rotor magnet 40 is attached to the rotating shaft member 20, and means for supporting the lower portion thereof by the stop ring 29 is provided. Used. In the motor 12, as in the case of the conventional motor, the stator coil 31 is inserted into the groove 3 provided in the base member 2a of the optical box 2 of the scanning device.
And a stator yoke 32, and a current of a predetermined frequency is supplied to the coil via a control circuit 35 to generate a magnetic field and rotate the rotor magnet 40.

A step 21 is disposed above the rotary shaft member 20 to which the rotor magnet 40 is attached, and the rotary polygon mirror 11 is mounted in contact with the lower surface of the step 21. The rotating polygon mirror 21 and the rotor magnet 4
0, a pressing spring 23 is arranged, and a rotor magnet 40 whose lower part is supported by a ring 29 and a rotating polygon mirror 11 whose upper part is locked to a stepped part 21 are vertically moved by a spring 23 respectively. , So that the supporting action on the rotating shaft member 20 is favorably exhibited.

As described above, the rotor magnet 40 constituting the drive motor is formed by integrally molding a plastic magnet into a disk shape, and a groove 41 is annularly formed on the surface of the rotor magnet 40. Set it up,
By attaching the balance weight 43 to the groove 41, the dynamic balance can be adjusted. When the motor is driven at a high speed of 8000 to 12000 RPM, or is a motor driven at a very high speed of 12000 RPM or more, a groove 42 is also provided on the lower surface of the main body of the rotor magnet, and By attaching the balance weight 43a to the groove 42,
The dynamic balance can be adjusted on two surfaces, and more precise dynamic balance can be adjusted. Further, a portion to be attached to the lower shaft of the rotor magnet 40 is configured as a step portion 44, and the step portion 44 corresponds to the ring 29 provided on the rotating shaft 20.

As described above, when a plastic rotor magnet is formed in a disk shape and grooves and the like are provided on its upper and lower surfaces, when the rotor magnet is rotated at a high speed, the centrifugal force of the rotation is obtained. Accordingly, stress concentrates on a step portion such as the groove, which is a weak point that destroys the rotor magnet. Therefore, in the rotor magnet of the present invention, the intersection between the bottom of the groove and the rising portion is not formed at a right angle, but the portion is formed in an arc shape. The arc-shaped portion is described using the reference symbol R in the figure, but by providing R on the side where a large stress is applied in each groove or step, the strength of the rotor magnet is reduced. Therefore, even when the rotor magnet is rotated at a high speed, it is possible to prevent the rotor magnet from being damaged by the centrifugal force. If there is no problem in the operation of attaching the balance weight to the groove, the corners of the groove and the step may be all curved surfaces.

In the rotating device 10 of the present invention configured as described above, the frame of the driving device is constituted by the base member 2a of the optical box 2 as in the case of FIG. , A fixed shaft 15 is fixedly held by a lower set screw 16 and upper and lower bearings 19, 19
The rotation shaft member 20 is rotatably supported with respect to the fixed shaft 15 via a. An upper ring 17 and a preload spring 18 are provided above the fixed shaft 15 to hold a bearing 19.

The rotating shaft member 20 rotatably supported on the fixed shaft 15 has a rotating polygon mirror 11 at an upper part and a rotor magnet 40 at a lower part. The motor 12 is constituted by the arranged stator coils 31. A stator coil 31 and a stator yoke 32 made of a magnetic material such as a silicon steel plate are arranged in the groove 3 provided in the base member 2a in correspondence with the rotor magnet 40 constituting the motor 12.

Then, a control circuit 35 is arranged for the stator coil 31, and a current is supplied at a predetermined pulse by switching (on / off) in the control circuit to drive the rotor magnet 40. When a current is applied to the stator coil 31 in the motor, a strong magnetic field is generated in the vertical direction in the drawing. However, by disposing the stator yoke 32 below the coil, the stator coil 3
1 is applied to the stator yoke 32
To return upward to perform the function of improving the efficiency of the motor. In addition to the above configuration, in the rotating device of the present invention, a groove 21a is also provided in the upper part of the rotating shaft member 20, and a balance weight is attached to the groove 21a to adjust the dynamic balance of the entire rotating body. It can be performed.

In the embodiment shown in FIG. 1, the case where the dynamic balance adjusting means is provided only for the rotor magnet 40 has been described. However, in the rotating device driven by using only the rotor magnet of the present invention. In the case where the outer diameter of the rotary polygon mirror is larger than the outer diameter of the rotor magnet, a means for attaching a balance weight for dynamic balance adjustment to the pressing spring 50 can be used as shown in FIG. When the rotor magnet is configured to be directly attached to the rotating shaft member without using an iron rotor member, and the rotor magnet is configured to have a large diameter, the rotor magnet is liable to be broken by the rotational centrifugal force. There is. Therefore, the rotor magnet 40 is configured to have a diameter as small as possible,
It is desired that even when rotated at a very high speed, there is no breakage due to centrifugal force generated during the rotation.

However, when the rotor magnet is configured to have a smaller diameter than the rotary polygon mirror, it is necessary to attach a balance weight using the grooves 41 and 42 provided on the rotor magnet 40 to adjust the dynamic balance. The problem of difficulty arises. Therefore, in the example shown in FIG. 2, the pressing spring 50 is configured to have a large diameter, and around the main body of the disc-shaped pressing spring 50,
The wall member 52 is provided so as to protrude downward. The pressing spring 50 is formed by using a conventionally used spring member having a large diameter, and a pressing portion 51 protruding from an upper portion of the main body urges the rotating polygon mirror 11 upward. , And performs an operation of positioning the rotary polygon mirror 11 and the rotor magnet 40.

By attaching a balance weight 53 or the like to the wall member 52 formed around the pressing spring 50, the dynamic balance of the rotating body can be easily adjusted. When the outer diameter of the pressing spring 50 is set to be slightly larger than the outer diameter of the rotor magnet and a groove-shaped gap is formed around the rotor magnet, a balance weight is attached to adjust the dynamic balance. This can be easily performed, and the rotating member can be made compact. Further, as described above, the pressing spring 5
When using a means for attaching a balance weight 53 for dynamic balance adjustment to 0, for example, it is possible to perform an operation of attaching the balance weight from the side while the rotating device is attached to the optical box. Become.

Therefore, in the rotating device constructed as shown in FIG. 2, a balance weight is attached to the rotor magnet via the groove 42 provided on the lower surface thereof, and the dynamic balance of the rotor magnet 40 alone is adjusted. In addition to performing the adjustment, the pressing spring 50 is also
It is possible to adjust the dynamic balance with respect to the rotating body by attaching a balance weight. Further, as shown in FIG. 1, when a groove is also provided on the upper surface of the rotating shaft member 20 and a means for attaching a balance weight to the groove is used, a more precise dynamic balance can be obtained. It is possible to perform the adjustment function, and together with the fact that the rotor magnet is made compact, the rotating body is 12000 RPM.
The above-described high-speed driving mechanism can be configured.

In the example of the rotating device shown in FIG. 2, the stator coil 31 disposed below the stator coil constitutes the motor 12 in combination with the rotor magnet 40. Then, as in the case of the example of FIG. 1, by supplying a current to the stator coil 31 by switching, the rotating polygon mirror is rotated at a high speed via the rotor member. At this time, when a current is supplied to the stator coil 31 by switching, a strong magnetic field output from the stator coil causes the stator yoke 32 to vibrate violently. However, in the example shown in FIG. 2, a cushioning material 33 such as sponge or rubber is arranged on the lower surface of the stator yoke 32 to reduce the vibration of the stator yoke 32 and to directly hit the bottom of the base member. You can choose not to do it. Therefore, as described above,
By providing a means for preventing the noise caused by the action of the stator yoke hitting the bottom of the groove when driving the motor, it is possible to prevent the generation of harsh noise to human ears when the motor is driven at high speed. It becomes possible to prevent. Further, the stator yoke can be provided so as to be embedded in the base member.

The rotating device constructed as described above can be used not only as a driving device for a rotary polygon mirror of an optical scanning device but also as a scanner motor in an image forming apparatus,
The present invention can be applied to other driving means. In addition, when the motor of the present invention is used for a drive motor driven at a relatively high speed, vibration and noise generated from the motor can be prevented.

[0030]

As described above, in the optical scanning device of the present invention, the driving motor does not use the conventionally used iron rotor member, but uses only the rotor magnet and the rotating shaft member. Since the driving type is used, the rotation mechanism can be simplified. In addition, since the iron rotor member is not used, it is possible to easily adjust the dynamic balance, and it is also possible to easily perform the assembling work of the device. Furthermore, when molding a rotor magnet made of plastic or the like, by forming the corners such as grooves into an arc shape, the strength of the member can be improved, and a rotating body that can withstand high-speed rotation is formed. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view of a rotating device of the present invention.

FIG. 2 is a cross-sectional view of another embodiment of the rotating device.

FIG. 3 is a side view illustrating a configuration of a scanning device used in a general image forming apparatus.

FIG. 4 is a cross-sectional view illustrating a configuration of a conventional rotating device.

Claims (1)

(57) [Claims] A light source for outputting a light beam containing information;
A rotating polygon mirror for polarizing the light beam in a predetermined direction and scanning light in the width direction of the image carrier such as a photosensitive drum, and a motor for driving the rotating polygon mirror;
A rotor magnet supporting the motor on a shaft member,
An optical scanning device comprising: a stator coil supported by a base member; wherein the rotor magnet is configured by a member shaped into a disk, and via a rotating shaft integrally provided with the rotor magnet,
An optical scanning device, comprising: a polygon mirror; and an annular groove for providing a balance weight for dynamic balance adjustment on the rotor magnet on two surfaces perpendicular to the rotation axis.